check the background program running in your computer.you can see on the right side bottom of your screen.that is cause also to slowdown your computer.to disable all of that click start button on the left side of your screen and then write MSCONFIG and then theres a small screen come out click STARTUP and then on the bottom disable all and restart your computer see if theres any changes.

if your pc slowdown check the the heat sink grease if its dried up. your pc slow down as it mean to say its overheating. no program can repair it. replace your heat sink grease. i recommend arttic silver 5